Roof construction



zmsma P. CHAPMAN ROOF CONSTRUCTION Filed Sept. 12, 1931 June 1%, W3.

8- aggqm/ I N VENTOR Patented June 1.8, 1935 {PATENT orris ROOF CONSTRUCTION Paul Chapman," NewYork; Ni Y. Application SeptemberlZ, 1931, SerialNo. 562,535

10Claims;

This invention in roof construction provides an economical supporting construction for" the outside roof covering of a peaked roof, and an unobstructed space beneath the roof for lighting and ventilation.

Referring to the' accompanying drawing, Fig. 1 is a perspective View of one of the hip rafters; Fig. 2 is an elevational View of the same. Fig. 3 is a plan view showing the means of adjusting the.

end of the said rafter horizontally. Fig. 4 is an elevational view showing the means of horizontal.

adjustment when the construction is adapted'to structures having supporting masonry wall enclosures. Fig. 5 is an elevational View of one of the hip rafters when the rafter is bent be.-

tween the peak and the caves to conform to the outline of the roof or for any other reason. Fig. 6 is a plan View of the construction adaptedto an approximately square or rectangularshaped'. Fig. '7 is a plan view of the construction adapted to an irregular shaped roof having eight of the aforesaid hip rafters. Fig. 8 is aplanview.

roof.

of the construction adapted to a roof .of rectangular form having one side much longer than the other.

Referring to Figs. 1, 6, '7, and-.8; a structural hip. rafter I extends diagonally downward from a peak'member 2" to avertical support 3. Jack rafters ta ib' upon which the roof covering-restsare. supported at their upper ends by the: hip rafter. Strut members 5b 50 support the lower endsof the jack rafters db and the upper ends of the rafters 6a. 6b, and are-themselves supported at their ends by the hip rafters I. The lower ends of the rafters 6a 61) rest upon the cave members in lb 'Ic id Te if. Referring to Fig. 2, L shaped members Ia support the ends of thestrut members baand also resist the compression in the bottom flanges'of the" The axes of the strut members at their ends. 1 bottom flanges of the struts 5a. intersect the axis of the rafter II as near to its bottom flange as practical, and a resultant upward reaction and a diagonal compression in the rafter I near and parallel to the bottom flange results from the compression in'the strut members 5a. The compression along the bottom flange of the rafter is transferred thru the member ID and is resolved into a vertical reaction in the support 3- (Fig. 1) and tension in both of the diagonally intersectingmembers la (Fig. 1). By constructively locating the compressive stresses in the rafter i and the struts Ea along their bottom flanges, negative bending moments are produced which reduce the positive bendi moments due to theirvertical loads-and result in economy of material. The-upper end of the rafter I is connected to the peak member 2 by a connection piece Ic rigidly connected to the rafter and boltedto the piece 2-. The ends of the rafter 'I arereduced in depth to clear other parts and.

strengthened: bycutting wedge shaped pieces fromthe ends of the web and then bending the top flange downwardand welding to the bottom portions alongv the-lines Id and I e.

Whentheconstruction is loaded, the bottom.

flange-of the rafter Itends to describe a slight convex are due to the elastic deformation of the stressed members. This condition is compensatedforby either. increasing the length of the struts 521 from their normal. lengths and decreasing the lengths of the, members la. likewise to. allow for deformation, and. drawing the top ends of the rafters Iagainst the peak pieces 2 by meansof'the bolts to. fitting into holes in thesaid peak pieces; or by forcing the lower end of' the rafter inward by the use of the U shaped bolts 'I'g with threaded nuts in forced against angles 'llc rigidly'attached to the diagonally'intersecting members 7a., as shown in Fig. 3.

Referringto' Fig: i, the construction is adapted to 'masonrywall support, and the ends of the rafters I- rest upon and are rigidly attached to plates'linloosely held in position on top of the wall- 3'w by anchor. bolts 3b with threaded nuts and washersextending thru holes in the plates 1m of asize' sufficient' for the required movement. Rodsln extending between the adjacent plates 1m under the ends of the adjacent rafters I, have threaded nuts T1) at their ends which are forced against structural angles 'ir rigidly attachedlto: the: plates 'l'm in order to force the end'softhe rafters I inward horizontally. This method: also compensates for the deflection of the rafter I1when the'structure is loaded.

Referring; to. Fig. 5, whereon account of its bent shape the rafter I isbuilt up of a plate I f and two top angles [g and two bottom angles Ih,

the same methods of compensating for deflec- 50, a tension polygon by the eave members 10 1d 7e if Is, the lower portion of the rafters l form compression members connecting the apices of the said polygons, and the amount of stress in the peak member 2 can be regulated. An additional polygon is formed by the members 5d 5e connecting the rafters l horizontally between the connections of the struts 5a 50 and the peak 2. This adaptation of the construction is suitable for roofs covering large areas.

Referring to Fig. 8, by the same methods as heretofore, a compression rectangle is formed by the struts 5a 5b, a tension rectangle by the eave members Ia lb, the lower portions of the rafters I form compression members connecting the apices of the said rectangles, and the amount'of stress in the two peak members 2 can be regulated. An additional horizontal member 21) fixedly connecting the peak members 2 transfers the horizontal stress transferred intothe peak members 2 by the rafters i. When the loads carried by the construction are unsymmetrical about the short axis of the rectangular roof, members 20 rigidly connecting the peak members 2-with the strut 5b, transfer vertical reactions between the peak members.

Referring to Fig. 6, the procedure in designing is hereafter outlined. The vertical deflection of the point of intersection of the strut members 5a with the hip rafters l, is calculated for the two systems of supporting members by first considering the peak member 2 loosely connected and the strut members 5a in compression, and then next by considering the strut members 511. to transfer shear only to the hip rafters l. The portion of the total load supported by each system is inversely proportional to the deflections thus found, provided that all the stressed members are of normal lengths. The first system produces a negative bending moment in the hip rafter I whereas the second system produces a positive moment, so that the resultant moment for which the hip rafter is designed becomes smaller, with resultant economy. A further possible economy may result by making a normal gap between the ends of the hip rafters l and the peak member 2,

and then forcing these members together by tightening the bolts 2a Fig. 2, which operation increases the negative bending moment in the hip rafters i. If desired, instead of the foregoing, a positive bending moment in hip rafters I may be added by making the hip rafters l longer than normal so that the peak member 2 must be forced a into position by loosening the bolts 1g Fig. 3.

The stresses produced by either of the foregoing operations are calculated by multiplying the stresses caused by a unity horizontal load applied at the peak member 2, by the ratio of the horizontal displacement occurring in the operations to that of the unity load, the peak member being assumed to be loosely connected.

An adaptation of my invention referred to in Fig. 6 follows. The members 5a are increased in length and la decreased to compensate for stress deformation, so that under full dead load the member 2 loosely fits in place. Negative bending moments then exist in the members I where the members 512 connect, and after the member 2 is rigidly attached, the positive moments from the live load cancel a portion or all of the negative moments. The bending moments are the major factors in designing the members I, and my invention affords a skilful designer an opportunity to effect great economies.

I claim:

1. In roof construction, a peaked four-sided framework supporting a roof, four hip-rafters extending from the peak to the eave-corners of the said framework, four eave-members forming the perimeter of the said framework, four compression struts with their ends rigidly attached to the said hip-rafters and forming a compression quadrilateral between the eaves and peak of the said framework, a peak member connecting the four said hip-rafters together.

2. In roof construction, a peak-ridged foursided framework supporting a roof, four hip-rafters extending in pairs from each end of the peakridge to-the eave-corners of the said framework, four eave-"nembers forming the perimeter of the said framework, four compression struts with their ends rigidly attached to the said hip-rafters and forming a compression quadrilateral located between the eaves and peak-ridge of the said framework, a horizontal peak-ridge member connecting the top ends of the two pairs of said hip- 1 rafters, diagonal members in the plane of the roof attached at one end to the said, peak-ridge member and at the other end to one'of the said compression struts, the said diagonal members providing means for transferring vertical loads from one end of the peak-ridge member to the other, substantially as described.

3. In roof construction, a peaked plural-sided framework supporting a roof, plural hip-raftersa each extending from the peak to one of the eavecorners of the said framework, plural eave-members forming the perimeter of the said framework, compression struts with their ends attached to the said hip-rafters consecutively and forming a compression polygon located between the peak and eaves of the said frame- 1 and the said compression struts substantially as described.

4. In roof construction, a peaked plural-sided framework supporting a roof, with a polygonshaped ridge extending around the said roof between the peak and the eaves, plural hip-rafters bent to conform to the said ridge and extending from the peak to the eaves of the said framework, compression struts with their ends attached to the said hip-rafters consecutively and forming a.

compression polygon located substantially at the said ridge, a peak member connecting the top ends of the said hip-rafters together plural eave members forming the perimeter of the said framework, all the foregoing members being means to support the roof by the combined action of the said bent hip-rafters and the said compression struts substantially as described.

5. In roof construction, a peaked plural-sided framework supporting a roof, plural hip-rafters each extending from the caves to the peak of the said framework, compression struts with their ends attached to the said hip-rafters consecutively and forming a compression polygon located between the peak and caves of the said framework, a peak member connecting the top ends of the said hip-rafters together, eave-members forming the perimeter of the said framework, bolts with adjustable screw-threaded nuts attaching the said hip-rafters to the said peak carried by the said compression struts and the said peak member, substantially as described.

6. In roof construction, a peaked plural-sided framework supporting a roof, plural hip-rafters each extending from the peak to the caves of the said framework, compression struts with their ends attached to the said hip-rafters consecutively and forming a compression polygon located between the peak and caves of the said framework, a peak member connecting the top ends of the said hip-rafters together, eave members forming the perimeter of the said framework, connection pieces attaching the said compression struts to the said hip-rafters through the bottom flanges of the said compression struts and directing the compressive force along the bottom flanges of the said compression struts to compensate for the bending moments in the compression struts under applied loads, the said connection pieces being means to reduce the deflections and the amount of material necessary for the construction of the said compression struts, substantially as described.

7. In roof construction, a peaked plural-sided framework supporting a roof, plural hip-rafters each extending from the peak to the eaves of the said framework, compression struts with their ends attached to the said hip-rafters consecutively and forming a compression polygon located between the peak and the caves of the said framework, a peak member connecting the top ends of the said hip rafters together, eave members forming the perimeter of the said framework, connection pieces attaching the said compression struts to the said hip-rafters near the bottom flanges of the said hip-rafters and connection pieces attaching the bottom flange of the said hip-rafters to the said eave members in order to direct the compressive forces along the bottom flanges of the said hip-rafters and reduce the bending moment in the hip-rafters from the applied loads, the location of the said connection pieces providing means to reduce the deflection and the amount of material necessary for the construction of the said hip-rafters, substantially as described.

8. In roof construction, a peaked plural-sided framework supporting a roof, plural hip-rafters each extending from the peak to the caves of the said framework, a peak member connecting the top ends of the said hip-rafters together, eave members forming the perimeter of the said framework, compression struts with their ends attached consecutively to the said hip-rafters and forming plural compression polygons at desired levels located between the peak and the eaves of the said framework, a tension polygon formed by the said eave members at the cave level.

9. In roof construction, a peaked plural-sided plural-ridged framework supporting a roof, plural hip-rafters bent to conform to the plural ridges of the said framework and extending from the peak to the eaves of the said framework, compression struts with their ends attached consecutively to the said hip-rafters and forming plural compression polygons substantially at the levels of the said ridges, a peak member connecting the top ends of the said hip-rafters together, eave members of the said framework forming a tension polygon at the cave level.

10. In roof construction, a peaked plural-sided framework supporting a roof, plural hip-rafters extending from the peak to the caves of said framework, a peak member connecting the said hip-rafters together, compression struts with ends attached to the said hip-rafters and forming polygons between the peak and eaves, and means to fix the proportionate load carried by the peak member and the compression struts by compensating for stress deformation substantially as described.

PAUL CHAPMAN. 

